The invention relates generally to extruding an elastomer. More particularly, the invention relates to an automatic elastomer extrusion apparatus and a method for extruding an elastomer onto a rotor or inside a stator of a progressive cavity motor or pump.
Progressive cavity pumps or motors, also referred to as a progressing cavity pumps or motors, typically include a power section consisting of a rotor with a profiled helical exterior surface disposed within a stator with a profiled helical interior surface. The rotor and stator of a progressive cavity apparatus operate according to the Moineau principle, originally disclosed in U.S. Pat. No. 1,892,217.
In use as a pump, relative rotation is provided between the stator and rotor by any means known in the art, and a portion of the profiled helical exterior surface of the rotor engages the profiled helical interior surface of the stator to form a set of sealed chambers or cavities. As the rotor turns eccentrically within the stator, the cavities progress axially to move any fluid present in the cavities.
In use as a motor, a fluid source is provided to the cavities formed between the rotor and stator. The pressure of the fluid causes the cavities to progress resulting in relative rotation between the stator and rotor. In this manner fluidic energy can be converted into mechanical energy.
As progressive cavity pumps or motors rely on a seal between the stator and rotor surfaces, one of or both of these surfaces preferably includes a resilient or dimensionally forgiving material. Typically, the resilient material has been a layer of elastomer disposed on the profiled helical interior surface of the stator, but can be disposed on the profiled helical exterior surface of the rotor. The stator and rotor are typically made of steel.
In use, the heat and stress encountered can cause cracking and other wear of the elastomer. A hydrocarbon or other caustic fluid can cause degradation of the elastomer. Regardless of the cause, it can be desirable to replace or otherwise automatically extrude a layer of elastomer on a profiled helical surface.